Method of continuously applying insulating material to a strand



June 17, 1941. E. R. TROCHE ETAL METHOD OF CONTINUOUSLY APPLYING INSULATING MATERIAL TO A STRAND I Filed Sept. 3, 1958 INVEN TORS E. R. TROCHE 1v. R.MORGAN A LAVANCURA 5r ATTORNEY Patented June 17, 1941 METHOD OF CONTINUOUSLY APPLYING INSULATING MATERIAL TO A STRAND Ernest R. Troche, Baltimore, Md., and Ivor N. R. Morgan, New York, N. Y., and Leo A. Vancura, Baltimore, Md., assiznors to Western Electric Company, Incorporated, New York, N. Y., a corporation New York Application September 3, 1938, Serial No. 228,356

(Cl. is -55) 2 Claims.

This invention relates to a method of continuously applying insulating material to a strand, and more particularly to a method of varying the compound pressure in the insulating head of a rubber covered wire machine during the starting and stopping operations.

In insulating conductors, and particularly conductors of low tensile strength, there is in some cases a high breakage during the starting and stopping of the insulating apparatus due to the high pressure of the insulating compound, as produced by a feed screw, being extruded upon the conductor being covered. The pressure of the compound created by such a feed mechanism varies in a different ratio during starting or stopping than the speed of the wire being covered, frequently resulting in a breakage of the wire.

An object of the present invention is to provide an effective and eflicient method of applying insulating compound to a strand in an extrusion apparatus.

In accordance with one embodiment of the invention, an adjustable core tube is provided whereby upon starting the extrusion or insulating operation the core tube may be moved for-' fully understood from the following description taken 1 in connection with the accompanying drawing, in which- Fig. 1 is a side elevation illustrating a. form of apparatus whereby the invention may be practised;

Fig. 2 is an enlarged sectional view taken on line 2-2 of Fig. 1; and

Fig. 3 is a graph illustrating by comparative curves the relationship between the speeds of thewire to be covered and the pressures of the insulating compound.

In the drawing an insulating head 9 of an extruslon apparatus is shown adapted to apply a coating of rubber compound or other material iii to a wire ii.

The wire is led from a supply reel i2 over a. sheave 13 into the extrusion apparatus. From the extrusion apparatus the newly coated wire is led to a chamber it to which steam or other heating medium is admitted through an inlet IE to vulcanize the insulating compound, the heating medium being maintained under pressure in this chamberf From the chamber the coated and vulcanized wire is led over a driven capstan i6 to a take-up reel i'l.

Referring to Fig. 2, the insulating head 9 is provided with a stationary bushing l8, which is held in position by set screw l9. One end of the stationary bushing i8 is threaded as at 20 to receive an adjustable plug 2|. This plug abuts againstpne end of a core tube holder 22, the opposite end of the core tube holder receiving and gripping the core tube 23. This core tube coopcrates with a fixed die 24. The rubber compound or other insulating material ii) is forced into and around the core tube and die by means of an Archimedean feed screw 25.

In the operation of the mechanism so far described, the wire ii is led from the supply reel i2 over a capstan i3 and is introduced into a longitudinal aperture 23 formed through the ad just'able plug 2!. Passing through the plug, the wire I! enters and passes through the core tube holder, the core tube, the die and into the heating chamber it.

It is expedient in this type of apparatus that the capstan for drawing the wire through the apparatus and the Archimedean screw for supplying the insulating material to the wire be mechanically coupled. It has been found, however, that when this is done the pressure of the insulating material due to the rotation of the feed screw rises more rapidly than the rate of speed of the wire. Referring, for instance, to Fig. 3, in which the abscissae indicate the speed of the apparatus and the ordinates indicate compound pressure, the curve A illustrates the relationship between the speed of the apparatus and the compound pressure when no adjustment is made in the core tube. The curve B indicates an ideal relationship in which the speed of the apparatus and pressure of the compound increase as a straight line function. The normal operating speed of the apparatus is at the point where the curves A and B intersect. It will be seen that with speeds lower than the normal operating speed of the apparatus, the compound pressure is too high, which in some cases results in a breakage of a wire, particularly when fine gage wire is being insulated.

It. has been found possible to remedy this condition by means of the adjustable plug abutting against one end of the core tube holder to obtain a pressure speed relationship as shown.- in curve B. It is possible, by means of the adjustable plug, to move the core tube holder and core tube forward within certain required limits during the starting operation, thereby reducing the orifice in the die to reduce the compound pressure while the apparatus is coming up to speed,

during which time the pressure would normally be too high. As the operating speed is being reached the adjustable plug is turned counterclockwise, and the pressure of the compound will force the core tube and core tube holdenbackward as the plug is withdrawn. v A similar procedure is'followed in bringing the apparatus to a stop. c

While the invention has been described with particular reference to a process and apparatus for' applying a rubber covering to wire, it will be readily understood that the apparatus, with suitable modifications, may be applied in various other relations. The scope of the invention is therefore limited only to the terms of the fol-- lowing claims.

' What is claimed is:

1. A method of applying a rubber compound to a wire in an extrusion apparatus having a die, a core tube cooperating with said die to form a restricted extrusion orifice, a driven take-up 1 means for drawing a wire through said core tube and die, and an Archimedean screw for deliverin: said compound to said extrusion orifice.

' ing a die, a core tube cooperating with said die to form a restricted extrusion orifice, a driven take-up means for drawing a wire through said core tube and die, and a driven feeding means for said compound which produces a compound pressure disproportional to its speed, which method comprises maintaining the speed ratio of said take-up and feeding means constant, and

varying the size of the extrusion orifice to compensate for the disproportionality of the compound pressure when the speed of the feeding means and take-up means changes.

ERNEST R. TROCHE. LEO A. VANCURA. IVOR N. R. MORGAN. 

